Dust Control Handbook for Industrial Minerals Mining and Processing

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Bailing airflow (Q B ) can be obtained from the drill manufacturer as the quantity airflow rating ofthe drill's compressor, which has units in scfm, while measurements of the collector airflow (Q C )can be reasonably made by using a hot wire anemometer, vane anemometer, or pitot tube at thecollector exhaust. More accurate measurements can be obtained by attaching a short (4-foot)duct extension to the collector exhaust and inserting the hotwire or pitot tube, to measure theairflow in cubic feet per minute (cfm), into a hole made at the halfway point in the duct. Thisextension can be simply made from cardboard and fitted to the outside of the collector exhaustduct. The collector airflow can be converted to scfm, but this is not necessary as the correctionsfrom the ambient conditions generally have a small effect on the measurement. Also, due to thechanges in the pressure drop across the filters caused by dust buildup, the quantity of air from thedust collector can vary by an amount that is much more significant than changes from standardatmospheric conditions.Common collector to bailing airflow ratios on operating drilling rigs were found to be as high as3:1 in the field. However, 2:1 ratios were more typical of operating collectors with normal filterloading [Page and Organiscak 2004]. Poorly operating collectors were found to operate at ratiosof 1:1 or lower. Testing has shown a notable reduction in dust concentrations escaping throughthe bottom of the deck shroud gap by increasing the dust collector to bailing airflow ratio[NIOSH 2006; Organiscak and Page 2005]. Figure 3.7 shows the results of changing the dustcollector to bailing air ratio at various drill deck shroud gap heights from the ground. As shown,the largest decrease in dust levels is observed when the dust collector to bailing airflow ratio isincreased from 2:1 to 3:1, with further decreases in dust levels as the ratio is increased to 4:1.Figure 3.7. Results of changing dust collector to bailing air ratio at various shroud gap heights.Airflow Maintenance for Dust ControlThe collector and bailing airflows need to be maintained to sustain the high collector to bailingairflow ratios that prevent high dust emissions. The bailing airflow from the drill's compressoris the maximum rated airflow and generally does not vary much over the life of the drill.Therefore, its impact on the collector to bailing airflow ratio is minor compared to the impact ofthe collector airflow. Performing the normal maintenance on the compressor as required by themanufacturer will keep it in proper operating condition.Drilling and Blasting 87
The collector airflow has a more substantial impact on the ratio due to the many components thatmake up the collector. The dust collector airflow can decrease over time through damagedcomponents and neglected maintenance. Therefore, proper maintenance of the collector tomaintain maximum airflow is required. Collector maintenance involves five actions by theoperator:ensuring that filter backflushing is operating properly and within specifications;verifying that the intake duct and collector housing are tightly sealed and free of holes;changing filters at recommended intervals or when damaged;ensuring that the tubing and inlet to the collector are free of obstructions; andensuring that the collector fan is operating properly and within its specified speed.Use of Collector to Bailing Airflow Ratios for Dust ControlThe collector to bailing airflow ratios are useful in that they form the basis of a model to predictthe relative severity of the drill dust emissions and to estimate how much of a reduction ispossible by measuring several basic parameters of the drilling operation. The parameters neededare: dust collector airflow (Q C ), bailing airflow (Q B ), drill deck shroud cross-sectional area (A S ),and shroud leakage area (A L ) or an approximate estimate for the leakage area [Page et al.2008a,b].The model depicted as a graph in Figure 3.8 (top) shows the relative reductions possible byreducing the leakage area [Page et al. 2008a,b]. To demonstrate how the graph can be used, thefollowing example is given.An operator has a drill rig with drill deck dimensions of 4 feet by 5 feet. The ratedcompressor Q B is 260 scfm and Q C was measured at 530 scfm which represents acollector to bailing airflow ratio Q C /Q B of approximately 2. The area of the shroud is2calculated by multiplying the width by the length resulting in A S = 20 ft . A L iscalculated by multiplying the leakage height (LH) in feet by the perimeter of the2shroud which results in A L = LH x 18 ft. Therefore, the ratio A S /A L = 20 ft /(LH x18 ft) and can be calculated by estimating LH.Since Q C /Q B = 2, the top graph in Figure 3.8 can be used to show how reducing theleakage gap between the shroud and the ground will reduce the severity of the dustconcentrations. A gap of 14 inches corresponds to A S /A L = 0.95, showing a relative3airborne respirable dust concentration of approximately 16 mg/m , while a gap of2 inches corresponds to A S /A L = 6.7, resulting in a relative airborne respirable dust3concentration of approximately 5 mg/m . This example demonstrates that reducingthe leakage height of the drilling operation will result in a substantial improvement indust reductions.It should be noted that any leakage area due to vertical shroud seam gaps should also be includedby estimating the area for vertical leakage and adding this value to the shroud leakage area (A L ),but many times vertical leakage may not be significant. Graphs for Q C /Q B greater than 2 aresimilar with the difference being that airborne respirable dust values at any value of A S /A L will88 Drilling and Blasting
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Report of Investigations 9689Dust C
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FUNDAMENTALS OF DUSTCOLLECTION SYST
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Minimizing Field Fits and Welds ...
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Recommendations for Proper Wet Dril
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CONTROL TECHNOLOGIES FOR FILLING 50
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Effective Filtration ..............
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ILLUSTRATIONSFigure 1.1. Relationsh
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Figure 3.2. The air and water flow
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Figure 9.5. Problem created by heat
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UNIT OF MEASURE ABBREVIATIONSUSED I
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Robert J. Franta, Quotation Enginee
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silica. Quartz is the most common s
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DUST CONTROL HANDBOOK FOR INDUSTRIA
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CHAPTER 1: FUNDAMENTALS OFDUST COLL
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The shape of particles affects how
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EXHAUST SYSTEMS DESIGNAll exhaust s
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stripping, which allows workers to
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When using the air quantities in Ta
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X = distance in feet from the face
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Checklist for Hood EffectivenessThe
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A major disadvantage of the high-ve
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A common misconception when designi
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Avoiding Mitered Elbows Greater Tha
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Figure 1.13. Depiction of the horiz
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Figure 1.14. Typical design of grav
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Baghouse CollectorsBaghouse dust co
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Table 1.2. Emission factors for cru
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Figure 1.17. Typical design of a me
Page 66 and 67: Reverse Jet (Pulse Jet) CollectorsR
Page 68 and 69: Figure 1.20. Cartridge collector wi
Page 70 and 71: Wet scrubbers are particularly adva
Page 72 and 73: Electrostatic precipitators normall
Page 74 and 75: may be related to specific applicat
Page 76 and 77: times. When considering the depth o
Page 78 and 79: Figure 1.25. Demonstration of how a
Page 80 and 81: Figure 1.26. A typical fan performa
Page 82 and 83: Fan TypesThere are two basic types
Page 84 and 85: Figure 1.30. Typical centrifugal fa
Page 86 and 87: Figure 1.32. Typical roof ventilato
Page 89 and 90: DUST CONTROL HANDBOOK FOR INDUSTRIA
Page 91 and 92: The vast majority of dust particles
Page 93 and 94: Table 2.1. Particle/droplet size in
Page 95 and 96: Air Atomizing NozzlesAir atomizing
Page 97 and 98: Hydraulic Flat Fan NozzlesFigure 2.
Page 99 and 100: for dust knockdown or suppression,
Page 101 and 102: Nozzle MaintenanceFigure 2.14. Typi
Page 103 and 104: Accidental DamageInadvertent harm t
Page 105 and 106: NDT Educational Resource Center, Io
Page 107 and 108: 78 Wet Spray SystemsDUST CONTROL HA
Page 109 and 110: contains a piston which delivers ha
Page 111 and 112: produce an increase in the penetrat
Page 113 and 114: Dry DrillingDry drilling is accompl
Page 115: Circular ShroudIn contrast to the u
Page 119 and 120: Air-Blocking ShelfThe air-blocking
Page 121 and 122: dust emissions from mast lowering,
Page 123 and 124: This simple procedure of creating a
Page 125 and 126: Figure 3.15. Air ring seal used to
Page 127 and 128: Figure 3.17. Illustrations showing
Page 129 and 130: unsubstantiated due to the inconsis
Page 131 and 132: safety considerations may preclude
Page 133 and 134: Figure 3.22. A filtration unit, loc
Page 135 and 136: Miller S, Emerick JC, Vogely WA [19
Page 137 and 138: USBM [1995]. The reduction of airbo
Page 139 and 140: 110 Drilling and BlastingDUST CONTR
Page 141 and 142: Wet Control MethodsPREVENTION AND S
Page 143 and 144: Figure 4.2. Examples of compressive
Page 145 and 146: Figure 4.5. Illustration of a dry (
Page 147 and 148: Figure 4.6. Illustration of a dry (
Page 149 and 150: Wet dust control methods for crushi
Page 151 and 152: Work Practices to Minimize Dust Exp
Page 153 and 154: Some specialty grinding operations
Page 155 and 156: should be frequently inspected for
Page 157 and 158: Open screen decks slowly to allow i
Page 160 and 161: DUST CONTROL HANDBOOK FOR INDUSTRIA
Page 162 and 163: CHAPTER 5: CONVEYING AND TRANSPORTT
Page 164 and 165: Figure 5.3. Basic depiction of mate
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that the material falls before land
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Figure 5.10. Skirtboard used within
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CarrybackMaterial that sticks or cl
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CONVEYOR DESIGN AND MAINTENANCE ISS
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Figure 5.15. Conveyor transfer encl
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High-volume, high-pressure sprays s
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Figure 5.19. Depiction of a bucket
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Figure 5.21. Depiction of two types
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Figure 5.25. Venturi eductor utiliz
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CHAPTER 6: BAGGINGThis chapter disc
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caused during manufacturing, includ
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Overall PerforationsThe use of over
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Figure 6.5. Open-top bag being load
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Bagging operators should be aware t
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Figure 6.8. Exhaust hood to capture
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In the original design, a single no
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The OASIS is a relatively simple de
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Figure 6.13. Bag storage shelves sh
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Figure 6.14. Bag and belt cleaner d
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other industrial application using
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The robotic arm automatic palletize
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For many years, this plastic wrappi
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warehouse location until a later ti
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used successfully to perform this c
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CHAPTER 7: BULK LOADINGDuring the b
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Figure 7.2. Loading spout discharge
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Cascading Loading SpoutFigure 7.5 i
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a seal at the entry and exit points
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REFERENCESBiere G, Swinderman RT, M
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200 Bulk LoadingDUST CONTROL HANDBO
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many years, as well as some new and
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Figure 8.2. Air spray manifold desi
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Figure 8.3. Test subject wearing po
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Spills of product material are a co
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epetitive dust leaks should not sim
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Effective Upward Airflow PatternThe
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Figure 8.8. Open-structure design c
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manually removing the bags and plac
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Figure 8.12. Increase in worker’s
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In other cases, an operation may wa
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Cecala AB, O'Brien AD, Pollock DE,
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224 Controls for Secondary SourcesD
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where C o = outside respirable dust
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minimal improvement in the cab's ai
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RECOMMENDATIONS FOR FILTRATION/PRES
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Effective FiltrationFigure 9.4. Res
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average decay times were between 16
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Figure 9.6. Filtration unit showing
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This table highlights a number of c
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NIOSH [2001b]. Technology news 486:
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upon the wind velocity (or disturba
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Maximum size is the largest particl
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Figure 10.4. Use of end-dumping wit
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conditions. Performance of each of
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A water truck, used to apply water
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Surfactants work by reducing the su
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which differed for the various site
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Figure 10.9. Self-tarping dump truc
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percent [Fryrear and Skidmore 1985]
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Figure 10.12. The armoring process
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A current method of stockpile forma
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Figure 10.15. Demonstration of how
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Chekan GJ, Cecala AB, Colinet JF [2
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Midwest Research Institute [1981].
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GLOSSARYAbrader. An implement used
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Carryback. Material that sticks or
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End-dumping. A process of spreading
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Open structure building design. A p
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Table bushing. A bushing used to se
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Delivering on the Nation’s promis
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